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I am learing comprehension and i can't figure out how to run a for loop a N amount of times. In this case I want to import the first 5 lines of a .csv file. But I want to understand the logic for further solutions.

 def columnMatch(self): with open(self.file_path) as csvfile: readcsv = csv.reader(csvfile, delimiter=';') line_count = 0 row_list = [] for row in readcsv: if line_count < 5: row_list.append(row) line_count += 1 return row_list
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  • As your code is currently, you want to break the loop once the criteria is exceeded. Commented Sep 15, 2018 at 11:28
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    Also, there is no list comprehension in your code Commented Sep 15, 2018 at 11:30
  • from itertools import islice and for row in islice(readcsv, 5): limits the loop to 5 iterations. Commented Sep 15, 2018 at 11:36
  • Thank you @MartijnPieters. I figured it out thanks to your comment: row_list = [row for row in islice(readcsv,5)] does the trick. Commented Sep 15, 2018 at 11:44
  • @Roy: so would row_list = list(islice(readcsv, 5)); no need to use a list comprehension when all the list comprehension does is echo the loop target. :-) (row is the loop target in your loop). Commented Sep 15, 2018 at 12:57

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You can use enumerate function to do it easier like:-

... readcsv = csv.reader(csvfile, delimiter=';') row_list = [] for i, row in enumerate(readcsv): if i < 5: row_list.append(row) else: break ...
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This would iterate over the remainder of the file without any need to do so.

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